Po308 help!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,556
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From: Cape Coral, Florida
Each coil pack has 4 wire...a 12 volt feed and a block or body ground...on the C5 all 4 coils on each bank are grounded at the back of the cylinder head...not sure on yours so maybe someone can chime in...the other 2 are a control wire (which sends a 0-5 volt square wave to fire the coil...the last is a low reference ground which is also at the PCM...I did a YouTube video not to long ago about functionally checking the coil...I'll post it here...there are also 2 connectors (C109/110) at the top by the center of the fuel rail...you can't miss it !!...these are where the 4 coil pack wiring comes together and then go to the PCM and the block ground.
Thread Starter
Intermediate
Joined: Jul 2019
Posts: 35
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After more checking I have found that just moving the wiring harness to the coils causes changes in the way the engine runs and makes it throw the po308 code I’ve been seeing. Is there a replacement harness for this.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,556
Likes: 4,026
From: Cape Coral, Florida
Yes, you can buy the set !!...check with maybe one of the vendors here or maybe Ecklers or some other Corvette parts supplier...I use GM Parts Warehouse !!...which wire do you think was causing the issue ??
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Intermediate
Joined: Jul 2019
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I’m not sure but there is definitely something going on. I just don’t feel like unwrapping 10 miles of tape to find it. Only to have it happen again. Would the new harness be just for coils or a complete engine harness
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,556
Likes: 4,026
From: Cape Coral, Florida
If you are talking about the harness from C110/109 down to the coil packs that you can buy...if you are talking about the harness that contains the injector wiring good luck !!...that also contains the ECT wiring. If you shook the wiring down it may also be the injector circuit...you just may have to unwrap the harness...so go grab a few beers !!...on the C5 at the back of the drivers side fuel rail is a bracket that causes chafing in that area..,working on a friends C6 recently I think they may have beefed up that section !!
Thread Starter
Intermediate
Joined: Jul 2019
Posts: 35
Likes: 0
I installed the new coil harness for bank 2 and unwrapped the fuel injector harness on the same side. I found 2 wires broken and touching one another. Fixed that. Still getting po308. I guess it’s time for the shop. Ugh
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